2001 Jeep Laredo

Transmission problem
2001 Jeep Laredo 6 cyl Four Wheel Drive Automatic 121000 miles

we drive and it will not shift to 3rd until I rev it almost till redline then it will drop into gear and when I stop again I gotta rev it all over again. Almost everytime it drops into gear when im reving it till 4 on the rpm scale, it never hits the red though and I put lucas in it and it does the same thing. I know I need a gov. Pressure sensor and trans temp sensor. Someone told me it wil be a $400 job and I dont think so. I would greatly appreciate it if you could tell me what to do, whats wrong, and what prices am I looking at.
thank you and
god bless
minister matthew russo
October 2, 2010.

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